chore: Item 11 — delete duplicate .md docs (keep canonical .adoc) (#33)

Removes **1** stale `.md` doc(s) that duplicate an existing canonical
`.adoc` sibling (estate convention: AsciiDoc canonical per RSR
template). Lossless: the `.adoc` is the maintained copy.

Deleted: \`CHANGELOG.md\` 


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Co-authored-by: hyperpolymath <hyperpolymath@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: hyperpolymath